HOW GLOBAL CHANGE AFFECTS SEED GERMINATION AND EMERGENCE IN LONGLEAF PINE ECOSYSTEMS
Date
2025-01-17Author
Bautista, Angelica
Department
Integrative Biology
Advisor(s)
Damschen, Ellen
Metadata
Show full item recordAbstract
Extreme precipitation events (periods of intense rainfall) are becoming more frequent in many regions as the climate changes. The amount and timing of precipitation are key drivers of seed germination and seedling emergence, yet the effects of extreme precipitation are still poorly understood. This knowledge gap is critical for understanding the composition and diversity of understory plant communities because changes to precipitation regimes may shift community composition over time due to alterations in germination and establishment patterns. Our study used a factorial greenhouse experiment to assess how extreme precipitation affected the germination and emergence of seven understory plant species native to longleaf pine (Pinus
palustris) ecosystems. We evaluated the effects of pulsed precipitation in conjunction with two other important drivers of seedling emergence and seedling survival - the depth of leaf litter and the presence of soil fungal communities. Leaf litter depth is strongly regulated by the fire regime, which historically included frequent, low-intensity fires every 1-5 years. We found that extreme precipitation and fungicide application did not affect seedling emergence or timing. However, increased litter depth strongly reduced seedling emergence. Despite changes in soil moisture due to pulsed precipitation, the herbaceous understory species examined here were still able to emerge. Given the negative impacts of deep leaf litter on seedling emergence, effective
ground-cover management may become essential for maintaining suitable microsites for seedling emergence. Additionally, species-specific responses to climate change highlight the need for management strategies tailored to each species' dormancy-breaking requirements. Future research is needed to better understand these species-specific cues.
Recruitment limitation is a key factor regulating community assembly and long-term ecosystem functioning, particularly in plants, where the transition from seed to seedling is one of the most vulnerable phases in development. In ecosystems like grasslands and savannas, which are known to be limited by seed arrival and establishment, changes in land use and disturbance regimes—especially fire—can significantly affect seed germination. However, these effects are complex, acting both directly and indirectly. Soil fungal communities can also influence establishment through various direct and indirect pathways. Yet, determining their impacts on establishment is difficult because these processes can operate in multiple ways, influencing each other in often unpredictable ways. We assessed how land-use history and altered fire regimes, along with their indirect effects on leaf litter depth and fungal communities, impact seed germination of four understory plant species native to longleaf pine (Pinus palustris) ecosystems. Our experiment differed in land-use history (post-agriculture or remnant) and fire regime (low vs. high fire frequency), manipulating litter depth and fungal presence (via fungicide) to
determine how their direct and indirect effects alter the seed germination probability. Despite their importance in structuring mature plant communities, we found that land-use history, fire regime, and fungicide application did not affect seed germination probability. Greater litter depth, however, increased germination across all species, highlighting the importance of local site conditions in creating optimal environments for seed germination. Soil fungal communities were influenced by land-use history but not fire regime. Since disturbance and the availability of suitable microsites are crucial for plant regeneration and seedling establishment, the next step in applying the implications of this work for managing longleaf pine ecosystems is to determine the ideal amount and type of litter that promotes seed germination and supports seedling growth.
Subject
Climate change, community assembly, seed, leaf litter, groundcover, restoration, land-use change, fire regime, community assembly, seed, leaf litter, groundcover, restoration
Permanent Link
http://digital.library.wisc.edu/1793/90779Type
Thesis